The present invention relates to substantially burglary-proof cylindrical locks, particularly to locks providing a high degree of protection against any attempt to pull-out the cylinder from the housing and/or to drill through the cylinder in order to disable the lock.
The conventional cylindrical lock includes a housing formed with a cylindrical bore; and a cylinder within the bore carrying locking elements movable to locking and unlocking positions with respect to the housing. The cylinder has an outer diameter equal to the inner diameter of the housing defined by the bore, such that the cylinder can be rotated to its locking and unlocking positions with respect to the housing. The cylinder is formed with a keyway for receiving a proper key in order to move the locking elements of the cylinder, and to rotate the cylinder, to its locking and unlocking positions with respect to the housing.
The conventional cylindrical lock is very vulnerable to breakage. For example, a common way of breaking such a lock is to force a foreign object, such a screw, into the keyway in order to firmly grip the cylinder, and then to forcibly remove the cylinder from the housing. Another technique is to drill into the cylinder in order to weaken or separate the locking elements from the cylinder.
A number of techniques have been devised in order to make such cylindrical locks more burglary-proof, but the known techniques are generally so complicated, expensive, and/or insufficiently effective.